Netflow packets are sent using UDP. A TCP client like telnet or a port scanner won't show an "open" port because the listener isn't designed to respond. You'd be better off installing a packet sniffer (if possible) on the receiving box to see if the Netflow packets are actually coming in.
If you want to know if the server really is listening on port 2055 run the following from the command prompt.
netstat -an | find "2055"
it should return the following result
UDP 0.0.0.0:2055 *:*
Hope this helps.